Dfe Tap Weight Calculator

Derive ideal additive DFE cancellation tap weights from measured main/postcursors under caller weight bound; assumes correct past decisions and excludes error propagation, tap quantization or adaptation.

Description

Ideal additive DFE weights cancel observed postcursor interference relative to a main cursor.

Ideal additive DFE weights cancel observed postcursor interference relative to a main cursor. Correct past decisions are assumed.^[1]

Enter a nonzero signed main cursor,1–128 finite postcursors and positive absolute caller bound. Return normalized weights and indexes strictly beyond the bound.

When to use Dfe Tap Weight Calculator

Use Dfe Tap Weight Calculator when you need to evaluate the supplied records under the calculation and evidence rules below. No adaptation, error propagation, quantization or automatic rejection of over-bound weights is modeled.

Prepare measured device or circuit evidence with matched frequency, temperature, waveform and calibration conditions. Supply explicit caller ratings and limits.

How to use Dfe Tap Weight Calculator and understand its results

Prepare measured device or circuit evidence with matched frequency, temperature, waveform and calibration conditions. Supply explicit caller ratings and limits.
Enter observedMainCursor, observedPostcursors, callerMaximumAbsoluteTapWeight using the field table and calculation rules, then run the tool.
Read idealDecisionFeedbackTapWeights, tapIndicesBeyondCallerLimit. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
observedMainCursor	Observed main cursor	number	Required
observedPostcursors	Observed postcursors	list of number	Required
callerMaximumAbsoluteTapWeight	Caller maximum absolute tap weight	number	Required

Enter a nonzero signed main cursor,1–128 finite postcursors and positive absolute caller bound. Return normalized weights and indexes strictly beyond the bound.

tap_i=−postcursor_i/mainCursor

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
idealDecisionFeedbackTapWeights	Ideal decision feedback tap weights	list of number
tapIndicesBeyondCallerLimit	Tap indices beyond caller limit	list of number

json

{
  "input": {
    "observedMainCursor": 2,
    "observedPostcursors": [
      0.5,
      -0.2
    ],
    "callerMaximumAbsoluteTapWeight": 0.5
  },
  "output": {
    "idealDecisionFeedbackTapWeights": [
      -0.25,
      0.1
    ],
    "tapIndicesBeyondCallerLimit": []
  }
}

Limitations and assumptions

No adaptation, error propagation, quantization or automatic rejection of over-bound weights is modeled.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Ffe Tap Weight Calculator: A finite causal zero-forcing FFE inverts the leading channel response. Truncation leaves a residual tail. For a complementary task, use Ctle Peaking Calculator: A normalized single-zero/two-pole CTLE transfer expresses frequency gain relative to DC. Pole and zero choices are caller parameters.

References

Dfe Tap Weight Calculator — tool.io

Similar or alternative tools

Ffe Tap Weight Calculator
A finite causal zero-forcing FFE inverts the leading channel response. Truncation leaves a residual tail.
Ctle Peaking Calculator
A normalized single-zero/two-pole CTLE transfer expresses frequency gain relative to DC. Pole and zero choices are caller parameters.